Abstract: Low frequency absolute calibration apparatus of acoustic vector hydrophone is studied and proposed. The theory of acoustic vector hydrophone absolute calibration is introduced. By measuring the acceleration of radiation surface on the bottom of the tube and using the distribution patterns of pressure and particle in the vertical direction in plane standing wave sound field, the calibration formula is obtained. The radiation surface of the calibration apparatus is improved, and the accelerometer for measuring radiation surface is calibrated. Finally, both the sensitivity and directivity of an acoustic vector hydrophone are tested by the absolute calibration apparatus. The results show that in the allowable error range of ±1 dB, the absolute calibration apparatus can be used for absolute calibration of acoustic vector hydrophone within the 10~315 Hz frequency range.